Conventionally, a paper cup having a trunk portion of a triply-walled structure disclosed the published of Japanese Utility Model Application No. 52-152043, as shown in FIG. 6 therein has been known as an insulated container of this type.
The paper cup of a triply-walled structure can be attained by wrapping an embossed paper sheet 11 around an outer surface of an inner container body 8 as an intermediate wall 9, and then pasting a paper sheet printed and colored with indicia, logos, or other printed material to explain goods on the embossed paper 11 as an outermost surface 10 of the cup.
An space between the outer surface of the inner container body 8 and the outermost surface 10, which is produced due to the embossment of the intermediate wall 9, acts as an insulated layer.
However, since this paper cup is of a triply-walled structure as described above, much material and many process steps such as an embossing step and a pasting step are needed, thereby increasing the production cost. In terms of physical characteristics of paper, the height of the embossment 11 is only about 0.5 mm, at most, so that a large space between the outer surface of the inner container body 8 and the outermost surface 10 is not achieved. If the height of the embossment 11 is increased, the paper becomes unusable because paper fibers are torn off. In the case of the above-mentioned cup of a triply-walled structure, when the user holds the cup in an extremely hot water-containing state by hand, the cup does feel so hot. However, there is not insufficiently large insulating space between the outer surface of the inner container body 8 and the outermost surface 10, so that the insulating capability of the above-mentioned paper cup is not high enough. In addition to that, although much material is used to produce the cup, rigidity of the cup is not sufficiently high and its grasping resistance is low. Accordingly, it is a principal object of the present invention to provide an insulated container having a simple structure, a high insulating capability, and a high grasping resistance, which can be manufactured at a low cost.